1. Field of the Invention
The present invention relates to a method for multiplexing data and control sequences and mapping the multiplexed sequences to a physical channel in a wireless mobile communication system.
2. Discussion of the Related Art
Data and control sequences transmitted from a media access control (MAC) layer to a physical layer are encoded and then provide transport and control services through a radio transmission link. A channel coding scheme is comprised of a combination of processes of error detection, error correction, rate matching, interleaving, and mapping of transport channel information or control information to the physical channel. Data transmitted from the MAC layer includes systematic bits and non-systematic bits according to the channel coding scheme. The non-systematic bits may be parity bits.
In the 3rd generation partnership project (3GPP), an uplink shared channel (UL-SCH) and a random access channel (RACH) of an uplink transport channel may be mapped to a physical uplink shared channel (PUSCH) and a packet random access channel (PRACH) of a physical channel, respectively. Uplink control information (UCI), which is one of an uplink control channel information, may be mapped to a physical uplink control channel (PUCCH) and/or a PUSCH. A downlink shared channel (DL-SCH), a broadcast channel (BCH), a paging channel (PCH), and a multicast channel (MCH) of a downlink transport channel are respectively mapped to a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), a physical downlink shared channel (PDSCH), and a physical multicast channel (PMCH) of a physical channel. A control format indicator (CFI), a hybrid automatic repeat request (HARQ) indicator (HI), and downlink channel information (DCI) of downlink control channel information are mapped to a physical control format indicator channel (PCFICH), a physical HARQ indicator channel (PHICH), and a physical downlink control channel (PDCCH) of a physical channel, respectively. The above transport channels are mapped to the respective physical channels through multiple processes. Especially, in a channel such as a UL-SCH, processing for cyclic redundancy check (CRC), code block segmentation, channel coding, rate matching, and code block concatenation is performed with respect to at least one transport channel or control information.
A process for processing a transport channel and/or control information is illustrated in FIG. 1. Data in the form of a transport block is input every transmission time interval (TTI). The transport block is processed as follows. A CRC attachment block attaches a CRC to the data in the form of a transport block. A code block segmentation block segments the CRC-attached data into one or more code blocks. A channel coding block performs channel coding for a code block data stream of each of the segmented code blocks. A rate matching block performs rate matching for the channel coded data stream. A code block concatenation block concatenates one or more rate-matched data streams to form a sequence of encoded data bits. Meanwhile, a separate channel coding block performs channel coding for control information to form a sequence of encoded control bits. A data/control multiplexing block multiplexes the sequence of encoded data bits and the sequence of encoded control bits, thereby generating a sequence of multiplexed bits.
One symbol may be comprised of at least one bit according to a modulation order (Qm). For example, for BPSK, QPSK, 16QAM, and 64QAM, one bit, two bits, four bits, and six bits corresponding respectively thereto constitute one symbol. In a system using single-carrier frequency division multiple access (SC-FDMA), one symbol is mapped to one resource element (RE), and therefore, a description can be given in units of symbols. Accordingly, the terms ‘coded data bit’, ‘coded control bit’, and ‘multiplexed bit’ may be replaced with the terms ‘coded data symbol’, ‘coded control symbol’, and ‘multiplexed symbol’, respectively, in consideration of the modulation order, for convenience of description. The terms ‘coded data bit’, ‘coded data symbol’, ‘coded data symbol’, ‘coded control bit’, and ‘coded control symbol’ may be abbreviated to ‘data bit’ ‘data symbol’, ‘control bit’ and ‘control symbol’, respectively, for convenience of description.
The control information may be classified into one or more types according to properties thereof and various multiplexing schemes may be considered according to the number of types.
If only one type of control information is present, when data information and control information are multiplexed, the control information may or may not overwrite the data information.
If two types of control information are present, the control information is divided into a first type of control information and a second type of control information. If the second type of control information is more important than the first type of control information, data information and control information may be multiplexed in a manner that the first type of control information overwrites or does not overwrite data information. Next, the second type of control information may or may not overwrite the multiplexed data information and/or the first type of control information.
A process of processing a transport channel for a UL-SCH of the 3GPP is illustrated in FIG. 2. FIG. 2 illustrates a matrix structure of ‘R’ rows by ‘C’ columns (R*C) (for example, C=14). Hereinafter, such a structure may be referred to as ‘a set of resource elements’. C successive symbols are arranged in a time area in a horizontal direction and R virtual subcarriers are arranged in a frequency area in a vertical direction. In a set of resource elements, virtual subcarriers are arranged adjacent to each other but subcarriers on respective physical channels corresponding to the virtual subcarriers may be discontinuous in the frequency area. Hereinafter, the term ‘virtual subcarrier’ related to a set of resource elements will be referred to as ‘subcarrier’ for brevity. In a normal cyclic prefix structure (‘normal CP structure’), 14 (C=14) symbols constitute one sub-frame. In an extended CP structure, 12 (C=12) symbols may constitute one sub-frame. That is, FIG. 2 is based on the normal CP structure. If the ‘extended CP structure’ is used, FIG. 2 may have a matrix structure in which C is 12. Referring to FIG. 2, M symbols (=the number of symbols per sub-frame×the number of subcarriers=C×R) may be mapped. Namely, M symbols may be mapped to M resource elements per one sub-frame. In addition to symbols generated by multiplexing data symbols and control symbols, reference signal (RS) symbols and/or sounding RS (SRS) symbols may be mapped to the M resource elements. Therefore, if K RS symbols and/or SRS symbols are mapped, (M−K) multiplexed symbols may be mapped.
FIG. 2 shows an example of mapping two types of control information, that is, control information 1 and control information 2 to a set of resource elements. Referring to FIG. 2, a sequence of multiplexed symbols is mapped by a time-first mapping method. That is, the sequence of multiplexed symbols is sequentially mapped from the first symbol position of the first subcarrier to the right. If mapping ends within one subcarrier, mapping is sequentially performed from the first symbol position of the next subcarrier to the right. Hereinbelow, a symbol may refer to an SC-FDMA symbol. The control information 1 and data information are mapped by a time-first mapping method in order of control information 1→data information. The control information 2 is mapped only to symbols located at both sides of RS symbols in order of last subcarrier→first subcarrier. The last subcarrier refers to a subcarrier located at the bottom of a set of resource elements of FIG. 2 and the first subcarrier refers to a subcarrier located at the top of the set of resource elements. The control information 1 rate-matches with data information and is mapped. The control information 2 punctures the data information and/or the mapped control information 1 and is mapped. The data information may be formed by sequentially concatenating multiple code blocks segmented from one transport block.
When multiplexing data information and control information, the following should be considered.
First, a multiplexing rule should not be changed by the amount and type of control information or presence/absence of control information. Second, when control information is multiplexed with data by rate matching or control information punctures data and/or other types of control information, the control information should not affect transmission of other data of a cyclic buffer. Third, a starting point of a cyclic buffer for a next redundancy version should not be influenced by presence/absence of control information. Fourth, in a hybrid automatic repeat request (HARQ) transmission scheme, HARQ buffer corruption should be able to be avoided. In a method for mapping multiplexed information to a data channel, a specific type of control information should be mapped to resource elements adjacent to an RS which can show good capability.
In the method of FIG. 2, since two types of control information are mapped to a virtual physical channel together with data information, a new rule is demanded to map another type of control information. In the method of FIG. 2, when the control information 2 punctures the data information and/or the control information 1, puncturing is performed from the last code block. However, if probability of generating an error in the last code block by transmission environments and a code rate is high, an error may occur only in the last code block. In that case, the error is detected after all code blocks are decoded, determination of a transmission error is delayed and power consumed to decode the code blocks is increased.